Magnetek MST E User manual

Brand: Magnetek

Model: MST E

Type: User manual

This manual is also suitable for

Plumbing Product MST E

MST/E Electric Shoe Brakes

Mondel MST/E Electric Shoe Brakes Instruction Manual

Part Number: 560022-R6

July 2006

SUPPLEMENTS FORMING PART OF THIS MANUAL:

DATE OF MANUFACTURE:

APPLICABLE DIMENSION PRINT:

EXPLODED VIEW:

PARTS LIST:

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Installation and Maintenance

Instructions

MST/E Electric Shoe Brakes

Table of Contents

Chapter 1.0: MST/E Electric Shoe Brakes Warnings and Cautions ...................................................4

Chapter 2.0: General Description........................................................................................................7

Chapter 3.0: Application....................................................................................................................10

Chapter 4.0: Description of Operation...............................................................................................11

Chapter 5.0: Installation ....................................................................................................................14

Chapter 6.0: Adjustment....................................................................................................................16

Chapter 7.0: Electrical Detail.............................................................................................................23

Chapter 8.0: Operational Test...........................................................................................................24

Chapter 9.0: Maintenance and Repair..............................................................................................26

Chapter 10.0: Replacement Parts.....................................................................................................32

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Chapter 11.0: Long Term Storage.....................................................................................................33

Chapter 1.0: MST/E Electric Shoe Brakes Warnings and Cautions

Read and Understand All Warnings And Cautions Printed In This Manual Before Commencing

Installation, Adjustment Or Repair

Chapter 5: INSTALLATION – Warnings and Cautions

Anyone involved in the installation or service of this brake must have:

• Received specific training.

• Had experience on similar equipment.

• Knowledge of the equipment on which the brake is installed.

• The ability to understand the terminology.

• The ability to understand the diagrams.

Do not proceed unless technically qualified for the work involved.

The integrity of the brake may be compromised or a replacement part may not fit if alterations are

made to the brake to achieve required alignment.

If the alterations to the brake supporting structure are required, they must be done under the

direction of a competent authority.

All electrical power to this equipment must be disconnected by competent personnel. Consult

specific wiring diagrams to identify and isolate all live power inputs to the equipment.

Unexpected movement or hazardous voltage can cause injury or death. Disconnect, lock out, and

tag out the power source that feeds this device to prevent power from being applied while

inspection and repairs are being performed. Before beginning repairs, try the operational controls

to verify that the intended power source is disconnected.

On a hoist, chock the drum to prevent any rotation, due to the effect of gravity on the hook block

etc.

On the travel motion subject to the effect of wind or camber gradient, apply the wind anchors or

otherwise secure the equipment against inadvertent movement when the brake is being worked

on or is removed entirely.

Never lift the brake assembly by the brake rod. The weight of the brake can irreversibly damage

the rod leading to fracture and total loss of braking effect.

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Failure to install the brake wheel correctly may result in total loss of braking. Do not operate the

brake unless the wheel is secured to the shaft.

Failure to properly center the brake and obtain uniform lining contact results in localized heating

and, ultimately, reduced torque, which can cause injury or death.

Chapter 6: ADJUSTMENT – Warnings and Cautions

Protect against the possibility of movement due to the effects of gravity, wind or other source of

energy, which has the potential to create a hazard when the brake is being worked on or is

removed entirely.

If the brake is arranged to operate in manual mode, the actuator “reserve stroke” must be

monitored and adjusted to be within the range of 30 to 35% of full stroke with the brake applied.

An actuator reserve stroke of zero will result in total loss of brake torque.

Under no circumstances should the brake be allowed to function with zero reserve stroke. Such

operation results in loss of load control, which can result in injury or death.

Always replace the caps on the actuator once adjustments are complete. This will prevent entry

of contaminants.

The optional automatic adjustment mechanism uses a one-way clutch to adjust brake shoe

clearance. It is located inside the clutch ring (R) shown in Fig.2A. Never disassemble this clutch.

Incorrect reassembly will render the auto-adjust feature inoperative. This can lead to loss of load

control and result in damage, injury or death.

If it is necessary to use a wrench to adjust the reserve stroke of a brake with auto-adjust, first

withdraw the drive pin (E) shown in Fig.2A and rotate the mechanism in the required direction. Do

not disturb the factory set pre-load, which is secured by set screws in nut (F). Releasing the

brake will take the load off of the brake rod thread and make it easier to turn.

The two setscrews used to lock nut (F), see Fig. 2A, to the clutch drive shaft, are factory set. Do

not loosen these setscrews or change the position of nut (F) with respect to the assembly. Failure

to observe this warning can cause the automatic adjustment feature to become inoperative. This

can lead to loss of load control and result in damage, injury or death.

Chapter 7: ELECTRICAL DETAIL – Warnings and Cautions

The actuator motor must be connected to its supply through a flexible cable or sealed flexible

conduit. This is required to ensure that contaminants will not enter the motor through the wiring

and junction box.

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Avoid contact with “live” terminals and prevent contaminant entry. Replace the terminal box

cover as soon as connections are complete.

Chapter 8: OPERATIONAL TEST – Warnings and Cautions

Always perform an operational test of the brake after any replacement, adjustment, or repair.

Read and understand the intent of the warnings published in this document – if in doubt, ask.

In a hoist application, post observers to monitor the position of the hook if it travels out of sight of

the operator.

Before conducting an operational test, remove all tools, chocks and other equipment, which may

create a hazard when the machine is operated.

Following any repair or adjustment, and before conducting an operational test, verify that all brake

adjustments are complete in accordance with Chapter 6.

Before attempting to operate any motion in any application, advise and account for the location

and security of all personnel involved.

Chapter 9: MAINTENANCE AND REPAIR – Warnings and Cautions

When replacing a brake wheel or associated drive line components on an existing installation,

verify that the brake is centered with uniform lining contact as described under the topic “Brake

Installation”. Incorrect repair or replacement can result in death or injury to personnel.

During operation, the actuator’s internal temperature and pressure will increase. This is normal

but presents a risk of burns and scalds if the filler plug is removed while the actuator is hot.

Switch off power to the actuator and allow it to cool to ambient temperature before checking,

topping off, or draining hydraulic fluid.

Improper brake operation and loss of load control due to incorrect brake adjustment can result in

death or injury to personnel. Under no circumstances is it permissible to allow the brake release

lever to bottom out against the hydraulic actuator.

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Chapter 2.0: General Description

2.1: Mondel type MST/E spring applied, Hy-Thrust actuated general purpose brakes are designed for

use on cranes and other severe braking applications in heavy industry. They can be used with

any drive type applied to hoisting or horizontal travel motions.

2.2: There are two basic models of this versatile, high-speed, AC operated brake: Type MST with

fixed value internal torque spring, and Type MST/E with an adjustable external torque spring.

2.3: The type MST brake spring is contained within the actuator. The brake can be arranged to

deliver a percentage of the maximum torque by rearranging the brake pivot pins to provide a

different lever ratio.

2.4: The type MST/E has an external torque spring, which is infinitely adjustable down to less than

50% of maximum torque.

2.5: Construction and operation of both models is similar; they are available for wheel sizes 6” to 16”.

A limited range of shunt-wound DC motor actuators is available.

2.6: A wide range of options is available; consult factory.

2.7: When the load cycle requires a larger than normal size, as is frequently the cause on crane

bridge drives, type MST and MST/E brakes can be provided with torques lower than traditional for

a given wheel size.

Except when specifically engineered and used in conjunction with Mondel Braketronic

Controllers, type MST/E are more suited to crane bridge brakes.

2.8: The type MST and MST/E brakes can be supplied as “drop-ins”, with footprints and shaft heights,

to replace a wide range of competitor’s brakes, including some metric sizes.

2.9: The standard actuator is weatherproof and dust proof. The electric motor is TENV construction,

and the hydraulic section is fully sealed and self-contained. Electric motors for certain hazardous

areas are available as options.

2.10: An optional breather unit can be installed to replace the standard filler plug for environments,

which experience large temperature swings. The breather prevents pressure build-up within the

actuator.

2.11: For more demanding environments, special hardware, enclosures, paint and surface treatments

are available.

IF YOU HAVE AN UNUSUAL APPLICATION, OR REQUIRE A RECOMMENDATION FOR A BRAKE

SIZE AND TYPE CONTACT MAGNETEK.

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Figure 1

General Arrangement

MST/E Electric Shoe Brake

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NOTE 1: FILL TO LOWER RIM OF

FILLER HOLE. USE ONLY FLUID

IDENTIFIED ON THE ACTUATOR

NAMEPLATE. DO NOT OVER-FILL

TORQUE ADJUSTMENT

SCREW (B)

BRAKE LEVER

DRIVE END

PIVOT

MANUAL

RELEASE

FILLER

PLUG

(NOTE 1)

OPTIONAL

TIME

DELAY

VALVES

FIXED

END PIVOT

HY-THRUST ACTUATOR

EXTERNAL TORQUE

SPRING

BRAKE

SHOES

PIVOT

BLOCK

BRAKE

ROD

LINK ARM

(ACTUATOR

END)

TERMINAL WIRING BOX

LINK

ARM

(OUTER

END)

Figure 1a

General Arrangement

MST/E Electric Shoe Brake

With Automatic-Adjustment and Automatic-Equalization

UTOMATIC

DJUSTMENT

(

)

BRAKE LEVER

DRIVE END PIVOT

MANUAL

RELEASE

FILLER PLUG

(

NOTE 1

)

OPTIONAL

TIME DELAYS

TERMINAL

WIRING BO

TORQUE

DJUSTMENT

SCREW

LINK ARM

(ACTUATOR END)

BRAKE

ROD

PIVOT

BLOCK

LINK ARM

(

OUTER END

)

BRAKE

SHOES

EXTERNAL

TORQUE SPRING

FIXED END

PIVOT

HY-TRUST

CTUATOR

UTOMATIC

EQUALIZATION

NOTE 1:

FILL TO LOWER RIM OF FILLER HOLE.

USE ONLY FLUID IDENTIFIED ON THE

CTUATOR NAMEPLATE. DO NOT

OVERFILL.

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Chapter 3.0: Application

3.1: The brake covered by this manual is type MST/E. This brake has an adjustable external torque

spring and is generally applied on installations where the required torque cannot be pre-

determined within well defined limits.

3.2: For a given wheel diameter the Association of Iron and Steel Engineers (AISE) determines the

prescribed torque, when applied to 30 and 60 minute rated motors in steel mill applications.

3.3: When applied to four quadrant drives or other applications where wheel heating can be

accurately predicted, type MST/E brakes can be provided with torque values in excess of the

AISE recommendations.

3.4: When the load cycle requires a larger than normal wheel size, as is frequently the case on crane

bridge drive, MST/E brakes can be provided with torques lower than AISE for a given wheel size.

3.5: For applications where larger than normal running clearance is required, a larger actuator can be

applied to a given brake. Typical would be severe applications where wheel expansion can be

considerable or where excessive wheel run-out can be expected.

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Chapter 4.0: Description of Operation

4.1: The brake is spring applied and actuator released. A heavy-duty compression spring within the

actuator pulls down on the brake lever and forces the shoes against the wheel.

4.2: The actuator piston rod extends when power is applied, the brake-shoe pressure removed and

running shoe clearance established.

4.3: Subject to the effect of brake geometry, braking torque depends upon three major factors:

4.3.(a): The diameter of the wheel.

4.3.(b): The coefficient of friction of the lining material.

4.3.(c): The force with which the linings are applied to the wheel.

4.4: Power applied to the actuator cancels the brakes ability to apply torque.

4.5: The force with which the linings are applied to the wheel depends on the spring length and

characteristics. Spring length increases as linings wear.

4.6: When the brake is released, Automatic Equalization of shoe clearance ensures equal clearance

between each shoe and the wheel.

4.7: Because the applied brake shoe force is proportional to the compressed length of the torque

spring, a slight decrease in brake torque occurs as linings wear (unless automatic adjustment is

used).

4.8: Adjusting the reserve stroke to its specified setting, restores the required spring force.

NEMA states: “The torque ratings apply at a worn lining condition defined as the point where re-

adjustment is required as recommended by the manufacturer”.

4.9: Automatic Equalization (AE) is available on all brakes of this class.

4.10: To understand how the automatic equalization works, it is important to recognize that the total

available shoe clearance is directly related to the length of active stroke and that the actuators

“Fully Released” position is the only consistent value for actuator stroke. The “Brake Applied”

position varies as the linings wear, resulting in a reduced “Reserve Stroke”. The “Brake Applied”

position also varies due to wheel expansion caused by temperature increase; this results in an

increased “Reserve Stroke”.

4.11: On brakes without Automatic Adjustment, after some significant lining wear and the brake wheel

close to ambient temperature, a reduction in the “Reserve Stroke” and a corresponding increase

in the “Active Stroke”, will be noticed. Corrective action will be necessary to ensure the minimum

reserve stroke. (See Chapter 6: “Actuator Stroke Adjustment / Brakes without Automatic

Adjustment).

4.12: On brakes equipped with the Automatic Adjustment (AA) option, the reserve stroke is maintained

by a one-way clutch mechanism arranged to shorten the effective brake rod length – but only

when adjustment is required – as follows:

4.12.(a): A retractable pin mounted on the brake lever, oscillates within a slot in the (AA) clutch

ring. (See Fig. 2A).

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4.12.(b): When the angle, through which the pin moves within the slot, does not allow contact

with the sides of the slot, nothing happens!

4.12.(c): When the brake applies, after some minimal amount of lining wear, the pin will contact

the side of the slot in the collar, which will advance the ratcheting mechanism and prepare for

adjustment the next time the brake is released.

4.12.(d): When the brake is next released and the load on the thread is minimal, the free wheel

set-up referred to in the previous paragraph will result in an advance on the thread when the pin

engages the other side of the slot in the collar.

4.12.(e): The ratcheting advancement will continue, a little at a time, until the pre-determined

reserve stroke is reached.

4.13: When the brake is released, the shoes are moved apart to provide running clearance from the

wheel. The actuator’s active stroke establishes the total clearance available for both shoes.

4.13.(a): As the brake releases, the shoe nearest to the actuator has been biased to open first.

This is done during manufacture, by inclining the actuator away from the nearest shoe (See Fig.

2).

4.13.(b): Clearance provided to the nearest shoe is restricted by the (AE) mechanism – located

on the base – which transfers the remaining clearance to the other shoe.

4.13.(c): As shoe wear occurs the friction bolt in the (AE) mechanism relocates to provide a new

reference point for the brake shoe on the actuator side of the brake.

4.13.(c).(i): The total available shoe clearance is determined by the active stroke.

4.13.(c).(ii): The clearance between the friction bolt and holes in the actuator links through which

it passes, determines the “actuator side” shoe clearance.

4.14: Various optional features are available, including latching hand release mechanisms, limit

switches, hydraulic and pneumatic overrides, etc. If the brake covered by this manual has any of

the optional features, they will be listed on the front page of this manual and covered by

supplementary instructions.

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4.15: The actuator for this series of Mondel Brakes can be supplied with optional, factory installed time

delays.

Figure 2

MST/E Brake Shown With Typical Brake Release Lever

Without Automatic Adjustment and Automatic Equalization

Figure 2A

MST/E Brake Shown With Typical Brake Release Lever

With Automatic Adjustment and Automatic Equalization

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CLUTCH DRIVE SHAFT

TANG, PIN (E)

COLLAR (C)

PIN (E)

BRAKE ROD

NUT (F)

ROTATOR COLLAR (R)

THIS SET SCREW AND ANOTHER 60 DEGS.

APART, ARE FACTORY SET TO MAINTAIN THE

INTEGRITY OF THE CLUTCH MECHANISM.

DO NOT DISASSEMBLE.

NOTE: TABLE 5 LISTS THE NEMA MINIMUM

RECOMMENDED LINING THICKNESS.

BRAKE LEVER IN RELEASED POSITION

BRAKE LEVER IN APPLIED POSITION

ACTIVE

STROKE

RESERVE

STROKE

SHOE CLEARANCE

EQUALIZING BOLT

SHOE CLEARANCE

EQUALIZING BOLT

TORQUE ADJUSTMENT SCREW (B)

TORQUE SPRING

SETTING SCALE

TOLERANCE +/- 1/32”

ON ALIGNMENT

BETWEEN BRAKE

HORIZONTAL

AND WHEEL

CENTER LINES

TOLERANCE +/- 1/32” ON ALIGNMENT BETWEEN

BRAKE AND WHEEL VERTICAL CENTER LINES

LOCK-NUTS (F)

(Not available on

MST/E with Automatic Adjustment)

(Shipping Bolt on

MST/E with Automatic

Adjustment)

Chapter 5.0: Installation

5.1: After unpacking, visually inspect the brake assembly to ensure that damage has not occurred

during shipment and that there are no loose or missing parts.

5.2: Prepare the brake support structure and install the brake assembly subject to the following:

5.2.(a): Allow adequate clearance between the brake and adjacent obstructions to allow access

for adjustment and maintenance.

Brake shoe replacement requires space for complete withdrawal of the link arm pivot pins.

5.2.(b): Whether mounting a brake in a new or existing installation, the base mounting bolts need

a reasonable clearance in the base mounting holes to allow the brake to be aligned for full

contact between the brake linings and the wheel.

5.2.(c): Circumstances may determine the best order of installation for the brake and the wheel.

This may be due to the available space or handling facilities on site; generally the wheel is

installed first.

5.2.(d): Center the brake shoes across the width of the brake wheel. This avoids ridge formation

and the possible creation of a dangerous situation as the linings wear.

5.3: Alternatively, it may be necessary to introduce the brake to the brake wheel from one side of the

wheel. In this case partial dismantling of the brake may be required depending on the

circumstances. Refer to the general arrangement and exploded view drawings in this manual to

evaluate the options.

5.3.(a): After installing the brake and wheel, make preliminary adjustments to apply sufficient

shoe pressure to raise the actuator piston rod ½” above its fully retracted position.

5.3.(b): This will apply the brake at approximately rated torque, causing the brake to square itself

to the wheel and maximize the shoe contact area, providing the bolt hole clearance will permit.

5.3.(c): When the brake assembly is correctly aligned and clamped to the wheel, loosen each of

the securing bolts in turn and verify clearance in the base mounting holes. This will ensure

tolerance to allow minor adjustment to the brake alignment to accommodate future relined shoes.

5.3.(d): For the reason identified in the previous paragraph Magnetek does not recommend

“Dowelling” or “Keeper Plates” to maintain alignment.

5.4: Type MST/E brakes are generally installed with the base horizontal and the brake wheel shaft

horizontal.

5.5: In most applications the brake can be installed from one side of the brake wheel. Alternatively it

may be necessary to partially dismantle the brake.

5.6: Type MST/E brakes can also be wall mounted, with the brake wheel shaft horizontal. This is only

possible if the actuator pump suction is flooded, which will be the case if the actuator hydraulic

section filler plug is at the highest point possible with the actuator horizontal. For this mounting

arrangement the actuator is best located above the wheel. The equalizing bolt opposite the

actuator will be most effective in ensuring equal shoe clearance.

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5.7: Type MST/E brakes can also be wall mounted with the brake wheel shaft vertical. Again this

requires the actuator hydraulic section filler plug to be at the highest point possible with the

actuator horizontal. For this mounting arrangement both equalizing bolts may be required to

ensure equal shoe clearance.

5.8: For any other mounting arrangements consult factory.

5.9: The brake assembly must always be square and aligned to the brake wheel within a maximum of

± 1/32 inch, in three axes (horizontal, vertical, and longitudinal).

5.9.(a): Adjust the brake support bracket to achieve the specified horizontal and longitudinal

alignment. For best performance, the brake base should be flat and parallel to the wheel rim or

motor shaft. It may be necessary to release and re-apply the brake pressure several times to

achieve optimum alignment. Shim under the brake base for the vertical alignment.

5.9.(b): When the brake assembly is correctly aligned and clamped to the wheel, check the

securing bolt clearance in each of the brake base holes. There must be clearance in the base

and through the brake support bracket to allow minor adjustments. Be sure that the brake shoes

are still aligned parallel to the face of the brake and that each brake shoe is fully secured to its

link arm.

5.9.(c): With the brake fully applied, verify that the shoes are centered on the wheel face and that

lining contact is within adequate bedding range.

5.9.(d): When the brake is correctly aligned in all three axes, tighten the brake mounting bolts

and re-check the alignment.

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5.10: Connect the actuator to the electrical supply using a flexible, sealed conductor, suitable for the

rated temperature. Use type “S0”, or higher temperature, cable. The actuator must be allowed

few degrees of movement without the risk of dirt or moisture entering the terminal box. Chapter 7

provides all necessary electrical details.

Chapter 6.0: Adjustment

6.1: Following any adjustment or repair of the brake, test operation of the brake as described under

“Operational test”, Chapter 8.

6.2: Complete adjustment is required following any rework where any settings were disturbed.

Table 1

BRAKE WHEEL

SIZES (Inches)

TYPICAL RUNNING

CLEARANCE

BETWEEN LINING

AND BRAKE

WHEEL (Inches)

MAXIMUM FULL

SPEED BRAKE

WHEEL run-out

(Inches)

0.014

0.016

0.020

0.026

0.032

0.038

0.006

0.008

0.010

0.013

0.016

0.019

Notes:

1. Refer to “Brake Installation” and “Replacing the Brake Shoes” for adjustment

instructions.

2. Evaluate brake wheel run-out at full speed. It must not exceed value shown in this

table.

6.3: Manual Operation

6.3.(a): Brake installation, shoe replacement, and actuator replacement, described elsewhere,

require the brake to be released and reapplied without energizing the actuator. When type “S”

Latching Hand Release is fitted, it can be used; or it can be manually over-ridden as follows:

6.3.(b): Brakes without Automatic Adjustment:

6.3.(b).(i): To manually release the brake: Adjust the brake rod hex-nuts – to increase the brake

rod length – reducing the “reserve stroke” until the piston rod is no longer visible. Continue

adjustment until there is sufficient lining to brake wheel clearance.

6.3.(c): To manually apply the brake: Adjust the brake rod hex-nuts – to decrease the brake rod

length – increasing the “reserve stroke” until the linings contact the brake wheel. Continue until

the brake release lever begins to rise. Proceed to “Actuator Stroke Adjustment”.

6.3.(d): Brakes with Automatic Adjustment:

6.3.(e): To manually release the brake: Refer to Fig. 2A, withdraw drive pin (E), then carefully

rotate the mechanism by hand to increase the brake rod length and, at the same time, reduce the

reserve stroke until the piston rod is no longer visible. Continue adjustment until there is sufficient

shoe/wheel clearance.

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6.3.(f): To manually apply the brake: Refer to Fig. 2A and withdraw drive pin (E), then rotate the

mechanism by hand to decrease the effective brake rod length until the linings contact the wheel

and the brake lever begins to rise. Proceed to “Actuator Stroke Adjustment”.

6.4: Actuator Stroke Adjustment

6.4.(a): When power is applied to the actuator the piston will be caused to extend. This will

compress the external spring and raise the brake lever to provide operating clearance between

the shoes and the wheel.

6.4.(b): When power is removed from the actuator, the spring will retract the lever until the shoe

pressure on the wheel prevents any further lever movement as the reserve stroke setting is

attained and the intended brake torque achieved.

6.4.(c): Brakes without Automatic Adjustment:

6.4.(d): Adjust the brake rod nuts until the brake release lever raises the piston rod to the

specified reserve stroke, (Table 2). Re-secure the brake rod nuts against the pivot block.

6.4.(e): Brakes with Automatic Adjustment:

6.4.(f): To make initial adjustment before engaging the auto adjust (AA), refer to Fig. 2A and

withdraw pin (E). Rotate the mechanism by hand to decrease the brake rod length until the

linings contact the wheel and the brake lever begins to rise. Continue adjustment until the

required reserve stroke is about 1/8” less than specified. Re-engage pin (E) allowing the (AA)

mechanism to complete the final stage of the adjustment process. This will verify that the

mechanism is operating correctly.

6.4.(g): Energize the actuator several times until the rotating collar (R) is no longer turned by the

(AA) drive pin (E). Verify that the reserve stroke is still at the desired value per Table 2.

Table 2

ACTUATOR

MAX

STROKE

(inches)

ACTIVE

STROKE

(inches)

DESIRED

RESERVE

STROKE (inches)

Ed23/5

1.97

1.27

0.7

Ed30/5

1.97

1.27

0.7

Ed50/6

2.36

1.56

0.8

Ed80/6

2.36

1.56

0.8

Ed121/6

2.36

1.56

0.8

6.5: Torque Adjustment

6.5.(a): The rated torque, as shown on the nameplate, will be developed when the following

conditions are met:

6.5.(a).(i): The brake is applied and aligned properly.

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6.5.(a).(ii): The actuator stroke is correct.

6.5.(a).(iii): The correct linings are fitted.

6.5.(a).(iv): The linings are in good condition and bedding is completed.

6.5.(a).(v): The brake wheel is aligned and in good condition.

6.5.(b): Torque adjustment for Mondel MST/E brakes is adjustable on site. Tighten or loosen

screw (B), see Fig. 2, to set the torque within the prescribed range shown on the scale. The

torque setting is obtained by matching the top of the spring-block to a line on the spring scale.

6.6: Automatic Equalization Assembly

6.6.(a): The total available shoe clearance is determined by the active stroke of the actuator.

Distribution of the resulting clearance is determined by two factors.

6.6.(a).(i): As the brake releases under power, the shoe nearest to the actuator has been biased

to open first. This is done during manufacture by inclining the actuator away from the nearest

shoe. (Fig. 2).

6.6.(a).(ii): Clearance provided to the nearest shoe is restricted by the (AE) mechanism located

on the base. The clearance between the friction bolt and holes in the base, through which it

passes, determines the “actuator side” shoe clearance.

6.6.(b): When the predetermined “actuator side” shoe clearance has been established, the

remaining clearance is transferred to the “non-actuator side” shoe.

6.6.(c): As lining wear occurs, the friction bolt in the (AE) mechanism is dragged to a new

location, to provide the reference point for the shoe clearance on the “actuator side” of the brake.

6.6.(d): The (AE) friction bolt mechanism is self-compensating after initial adjustments are

completed as follows:

6.6.(d).(i): Release the brake and, using a soft-faced mallet if necessary, force the actuator side

link away from the wheel. This will set the actuator side (inner) shoe to the maximum available

clearance.

6.6.(e): The actual clearance which will be allowed to the “actuator side” shoe is determined by

the difference in diameter between the friction bolt shank and the holes in the links, through which

it passes.

6.6.(f): The friction bolt assembly is pre-tensioned at the factory. DO NOT FIELD ADJUST. If

the friction bolt assembly is disturbed for any reason it can be retensioned as follows:

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560022-R6

6.6.(g): Refer to Fig. 3a: Install friction bolt through Automatic Equalization arms and base. Add,

onto the end of the friction bolt, a stack of three Belleville washers in series, (as indicated below),

followed by a plain flat washer.

6.6.(g).(i): Install a castle nut, tighten nut until the flat washer is

FLUSH with the side of the

Automatic Equalization arm. Loosen or tighten the nut no more than 1/8 of a turn, only enough to

align the nearest cotter pin slot and hole. Install the cotter pin. This completes the assembly.

6.7: Shoe Clearance Adjustment

6.7.(a): The total available shoe clearance is determined by the active stroke of the actuator and

the brake lever ratio. Distribution of the resulting clearance is determined by the setting of the

active shoe clearance equalizing bolt (Fig. 2).

6.7.(b): Generally only one of the two equalizing bolts will be effective depending on the lever

ratio arrangement and subject to the brake being installed horizontally or vertically.

6.7.(c): The “active” equalizing bolt will be evident after energizing the actuator.

6.7.(d): To equalize the brake shoe running clearance:

6.7.(d).(i): Back-off both equalizing bolts and energize the actuator allowing the shoes to move

away from the wheel.

6.7.(d).(ii): Adjust the active side equalizing bolt to limit the travel of that shoe; this moves the

other shoe away from the wheel. Continue adjustment until wheel clearance is equal for both

shoes.

6.7.(d).(iii): Set the non-active side equalizing bolt so that shoe travel is not restricted; lock both

equalizing bolts with jam-nuts.

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560022-R6

(AE) ARM SIDE

CASTLE NUT SIDE

6.8: Parallel Shoe Gap Adjustment

6.8.(a): For optimum lining wear distribution, brake shoes have controlled freedom to align with

the wheel contour as the linings wear.

6.8.(b): Each brake shoe holder pivots on its link arm. Its freedom to rotate under gravity is

controlled by a shoe holder friction mechanism.

6.8.(c): Spring loaded pins in each link arm bear against the inside of the shoe (Fig. 3). This

provides tension to maintain shoe alignment when the brake is released. The tension is not

adjustable. When a shoe is replaced make sure that both shoe alignment tension mechanisms

are re-installed.

6.8.(d): To align shoes with the wheel, apply the brake at the rated torque and make the

following initial adjustments:

6.8.(d).(i): Release the brake manually or under power.

6.8.(d).(ii): With the brake released, use a soft-faced mallet to tap the upper edge of each brake

shoe, in towards the wheel, in the direction it would rotate under gravity.

6.8.(d).(iii): Re-apply the brake, and the shoes will be forced to align with the wheel to optimize

parallel clearance with the wheel.

6.9: Time Delay Adjustment

6.9.(a): The actuator nameplate will indicate when optional time delay valves are installed.

6.9.(a).(i): Letter “S” indicates an adjustable piston retract, (brake application), time delay.

6.9.(a).(ii): Letter “H” indicates an adjustable piston extend, (brake release), time delay.

6.9.(a).(iii): If both letters “S” and “H” are present, then the actuator is equipped with adjustable

time delay valves independently controlling both the piston extend and retract times.

6.9.(a).(iv): When time delay valves are not fitted, the actuator response time to extend or

retract, is between 0.4 and 0.8 seconds depending on actuator size

6.10: With time delay valve(s) installed, the extend and/or retract times are adjustable between

approximately 0.5 and 10 seconds depending on actuator size.

6.10.(a): Remove the delay valve protective cap to expose the adjustment screw. For minimum

delay set the screw head flush with the housing. Fig. 1 shows valve location.

6.10.(a).(i): Turn the screw clockwise to increase, and counter clockwise to decrease the delay.

Note: The standard actuator has the shortest response time. An actuator fitted with delay(s)

provides longer response times, even when the delay(s) are adjusted for minimum effect.

8/17/2006 Page 20 of 33 MST/E Electric Shoe Brakes Manual

560022-R6

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